Synchronous switching of digital audio while maintaining block alignment

Abstract

A system and method for synchronous switching of digital audio data channels while maintaining block alignment between the switched digital audio signals at an output separates status and user bits from audio data and validity bits for each digital audio signal, storing the status and user bits in respective memories for each digital audio data channel. The audio data and validity bits for each digital audio data channel are input via a data first-in, first-out buffer to an audio multiplexer. The status and user bits from the memories for each digital audio data channel are read out by a system clock in synchronization with a system block signal and input to a status/user multiplexer. A selector provides control signals to the multiplexers to select the digital audio data channel to provide to an output transmitter. The status and user bits are combined with the audio data and validity bits in the output transmitter in synchronization with the system block start signal to provide a digital audio signal output that maintains block alignment between the switched digital audio signals at the output.

What is claimed is: 
     
       1. A system for synchronous switching between digital audio data channels comprising: for each digital audio data channel means for separating auxiliary data bits from audio data in a digital audio signal input organized in blocks of data;   for each digital audio data channel means for storing the separated auxiliary data bits; and   means for switching between selected ones of the digital audio data channels by switching between the auxiliary data bits from the selected digital audio data channels based upon a system block start signal and a user input select signal and between the audio data from the selected digital audio data channels based upon the user input select signal and a system frame start signal related to the system block start signal to provide an output digital audio signal that maintains block alignment for the auxiliary data bits when switching between the selected digital audio data channels.   
     
     
       2. The system as recited in claim 1 wherein the separating means comprises: for each digital audio data channel means for extracting a clock signal from the digital audio signal input; and   a separator having as inputs the clock signal and the digital audio signal input and providing as outputs the clock signal, the auxiliary data bits and the audio data.   
     
     
       3. The system as recited in claim 2 wherein the storing means comprises: means for generating an input enable signal from the digital audio signal input; and   a first-in, first-out (FIFO) buffer that is clocked by the clock signal when enabled by the input enable signal to store the auxiliary data bits.   
     
     
       4. The system as recited in claim 3 wherein the switching means comprises: a selector controller having as inputs the user input select signal for changing from one audio channel to another, the system block start signal and the system frame start signal and providing as outputs an auxiliary select signal in response to the system block start signal and the user input select signal and an audio select signal in response to the user input select signal and the system frame start signal; and   means having as inputs the auxiliary data bits from each digital audio data channel and the audio data from each digital audio channel for selecting one of the digital audio channels as the digital audio output in response to the auxiliary and audio select signals.   
     
     
       5. The system as recited in claim 4 wherein the selecting means comprises: an auxiliary multiplexer having as inputs the auxiliary data bits from the digital audio data channels that are clocked out from the FIFO buffer in response to a system clock and an output enable signal derived from the system block start signal, and being controlled by the auxiliary select signal to provide the auxiliary data bits at the output from the digital audio data channel indicated by the user input select signal;   an audio multiplexer having as inputs the audio data from the digital audio data channels and being controlled by the audio select signal to provide the audio data at the output from the digital audio data channel indicated by the user input select signal; and   an audio transmitter/encoder having as inputs the outputs from the auxiliary and audio multiplexers and the system block start signal and providing as an output the digital audio signal indicated by the user input select signal.   
     
     
       6. A method of synchronous switching between digital audio data channels comprising the steps of: separating for each digital audio data channel auxiliary data bits from audio data in a digital audio signal input organized in blocks of data;   storing the auxiliary data bits for each digital audio data channel; and   switching between selected ones of the digital audio data channels by switching between the auxiliary data bits from the selected digital audio data channels in response to a system block start signal and a user input select signal and between the audio data from the selected digital audio data channels in response to the user input select signal and a system frame start signal to provide an output digital audio signal that maintains block alignment for the auxiliary data bits when switching between the selected digital audio data channels.